Revert of [Android] Stop hiding the RWHV layer subtree when hiding the widget

Revert of [Android] Stop hiding the RWHV layer subtree when hiding the widget (patchset #12 id:330001 of https://codereview.chromium.org/1001573003/)

Reason for revert:
Speculative fix for blank display after cold startup.

Original issue's description:
> Reland "[Android] Preserve the front buffer when the activity is paused"
>
> This change was reverted in r322170 due to WebView breakage. The
> ApplicationStatus dependency has been made optional, allowing
> WebView to opt-out of its use.
>
> Original description: ----------------------------
>
> Currently, when an activity is stopped, we explicitly hide the
> foreground Tab. This is problematic, as current hiding semantics
> might clear the visual front buffer before the window is hidden.
> This in turn causes an unpleasant flickering during activity
> transitions, e.g., when backgrounding Chrome or locking the screen.
>
> Wire Activity onPause/onResume notifications to WindowAndroidObservers,
> allowing the foreground tab to preserve its front buffer while hiding
> its web content. If the tab is explicitly hidden, or the root window
> is lost, the front buffer will be cleared as usual.
>
> BUG=462752, 434401
>
> Committed: https://crrev.com/7954daf991a2adda234dc2e886b2d1ddf0049221
> Cr-Commit-Position: refs/heads/master@{#322228}

TBR=sievers@chromium.org,dtrainor@chromium.org,tedchoc@chromium.org,piman@chromium.org,boliu@chromium.org,torne@chromium.org
BUG=481450, 481115, 434401
Committed: https://crrev.com/631abee367dc1c119c559ef82e1601e790c2c37c
Cr-Commit-Position: refs/heads/master@{#327092}

[jdduke (slow), 2015-04-27 17:35:39]

Created Revert of [Android] Stop hiding the RWHV layer subtree when hiding the
widget

[jdduke (slow), 2015-04-27 17:47:54]

The CQ bit was checked by jdduke@chromium.org

[commit-bot: I haz the power, 2015-04-27 17:51:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1109863003/1

[commit-bot: I haz the power, 2015-04-27 19:04:24]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-27 19:05:14]

Patchset 1 (id:??) landed as
https://crrev.com/631abee367dc1c119c559ef82e1601e790c2c37c
Cr-Commit-Position: refs/heads/master@{#327092}